Method and apparatus for analysis using X-ray spectra

Abstract

A method for precisely measuring and displaying the whole profile of an X-ray spectral waveform, which rises from a background level and finally returns to the background level after passing across a peak. X-rays are counted for a time interval of to at a spectral position, resulting in X-ray N counts not containing statistical fluctuations. A standard deviation Eo representing a variation accompanying the N counts is given by Sqrt(N). Where the variation is greater than a given magnitude (tolerance error Er for display) at a spectral position where the X-ray intensity is high, X-rays are counted for a time interval of tm longer than the time interval to, producing increased counts Nm.

1. A method of X-ray analysis using an X-ray spectrum obtained by a wavelength-dispersive X-ray spectrometer that detects and spectrally disperses X-rays produced from a sample irradiated with a beam of charged particles or X-rays, said method comprising the steps of:
 making variable a time for which X-rays are counted at each spectral position; 
 converting obtained X-ray counts into X-ray counts to be collected per given count time in such a way that the magnitude of variation caused by statistical fluctuations of the X-ray counts to be collected per given count time is made equal to or less than a previously specified tolerance value at any spectral position; and 
 obtaining the X-ray spectrum using the X-ray counts obtained by the conversion. 
 
   
   
     2. A method of X-ray analysis as set forth in  claim 1 , wherein said X-ray spectrum is displayed based on the counts per given count time obtained by the conversion. 
   
   
     3. A method of X-ray analysis as set forth in  claim 1 , wherein said sample is analyzed quantitatively by using the counts per given count time obtained by the conversion as counts collected from characteristic X-ray peaks arising from elements contained in the sample. 
   
   
     4. A method of X-ray analysis as set forth in  claim 1  or  2 , wherein a reference count time for which X-rays are counted at the spectral positions is previously set, and wherein the count rates at the spectral positions are found from counts collected for the reference count time and from the reference count time. 
   
   
     5. A method of X-ray analysis as set forth in  claim 4 , wherein a time for which counting is continued at the spectral positions after passage of said reference count time is determined based on (i) said count rates at the spectral positions, (ii) said reference count time, and (iii) said tolerance value. 
   
   
     6. A method of X-ray analysis as set forth in  claim 4 , wherein said reference count time is used as said given count time. 
   
   
     7. A method of X-ray analysis as set forth in  claim 1  or  2 , wherein the X-ray wavelength axis of said X-ray spectrum or an axis corresponding to the X-ray wavelength axis indicates at least one of wavelength, energy, a spectral position indicative of the distance from a point at which X-rays are produced to the center of an analyzing crystal, the value of 2θ, the value of θ, and the value of sin θ, where θ is the scattering angle of the analyzing crystal. 
   
   
     8. An X-ray analysis apparatus using an X-ray spectrum obtained by a wavelength-dispersive X-ray spectrometer that detects and spectrally disperses X-rays produced from a sample irradiated with a beam of charged particles or X-rays,
 wherein a time for which X-rays are counted at each spectral position is made variable, 
 wherein obtained X-ray counts are converted into X-ray counts to be collected per given count time in such a way that the magnitude of variation caused by statistical fluctuations of the X-ray counts to be collected per given count time is made equal to or less than a previously specified tolerance value at any spectral position, and 
 wherein the X-ray spectrum is obtained using the X-ray counts obtained by the conversion. 
 
   
   
     9. An X-ray analysis apparatus as set forth in  claim 8 , wherein said X-ray spectrum is displayed based on the counts per given count time obtained by the conversion. 
   
   
     10. An X-ray analysis apparatus as set forth in  claim 8 , wherein said sample is analyzed quantitatively by using the counts per given count time obtained by the conversion as counts collected from characteristic X-ray peaks arising from elements contained in the sample. 
   
   
     11. An X-ray analysis apparatus as set forth in  claim 8  or  9 , wherein a reference count time for which X-rays are counted at the spectral positions is previously set, and wherein the count rates at the spectral positions are found from counts collected for the reference count time and from the reference count time. 
   
   
     12. An X-ray analysis apparatus as set forth in  claim 11 , wherein a time for which counting is continued at the spectral positions after passage of said reference count time is determined based on (i) said count rates at the spectral positions, (ii) said reference count time, and (iii) said tolerance value. 
   
   
     13. An X-ray analysis apparatus as set forth in  claim 11 , wherein said reference count time is used as said given count time. 
   
   
     14. An X-ray analysis apparatus as set forth in  claim 8  or  9 , wherein the X-ray wavelength axis of the X-ray spectrum or an axis corresponding to the X-ray wavelength axis indicates at least one of wavelength, energy, a spectral position indicative of the distance from a point at which X-rays are produced to the center of an analyzing crystal, the value of 2θ, the value of θ, and the value of sin θ, where θ is the scattering angle of the analyzing crystal.